<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<style>

body { white-space: pre-wrap; width: 1ch; font-family: monospace }
body:first-line { }

</style>

<script>

function boom()
{
  document.body.textContent = "\n\u202AX ";
  document.documentElement.offsetHeight;
  document.body.appendChild(document.createTextNode("Y"));
  document.documentElement.offsetHeight;
}

</script>
</head>
<body onload="boom();"></body>
</html>
